I honestly think it’s a very good trait in Tomoya to be so considerate of Tomoyo as to break up with her, even if she doesn’t want to herself. Tomoyo’s personal love just can’t be judged to be worth as much as the personal success she might have had without Tomoya.
They can’t be together due to the vast differences in where they should both inevitably end up in the first place for political reasons. Maybe you remember
(after story) the after story, where Tomoya doesn’t get his promotion because his father was dealing drugs? If she were to become some company chairman or try to get into politics, being married to some dumb deadbeat isn’t going to work out for her.
The painful rumours in school and her own lack of discipline in dealing with Tomoya is just a foreshadowing of what might happen if she tries to drag Tomoya with her to the top. Tomoya knew that Tomoyo would obviously choose him over anything else, so he would undeniably be getting in the way of her personal success. He breaks up with her because he too values her personal success more than their love. And I think that’s a great thing.